Photographic bleach-fix solutions

ABSTRACT

Compositions which are effective as photographic bleach-fixes can be prepared from solutions containing substantial amounts of reduced oxidant, e.g., ferrocyanide, and dissolved silver by reaction with iodine which oxidizes the reduced oxidant and precipitates silver as silver iodide. This can be used for effective regeneration of photographic bleach-fix compositions.

United States Patent 2,944,895 7/1960 West et al..... 6/60 3,170,793 2/1965 Levy 96/61 FOREIGN PATENTS 933,008 7/1963 Great Britain 96/60 BF OTHER REFERENCES Bard, Charleton C. and Julius C. Battaglini, Regeneration of Photographic Silver Bleach Solutions," Defensive Publication (U.S. Patent Office), 862 0.6. 23 (May 6,1969) Primary Examiner--William D. Martin Assistant Examiner-Raymond M. Speer Atlorneys-W. O. Hodson, P. R. Holmes and Dwight .1. Holter ABSTRACT: Compositions which are effective as photographic bleach-fixes can be prepared from solutions containing substantial amounts of reduced oxidant, e.g., ferrocyanide, and dissolved silver by reaction with iodine which oxidizes the reduced oxidant and precipitates silver as silver iodide This can be used for effective regeneration of photographic bleachfix compositions.

PHOTOGRAPHIC BLEACHJIX SOLUTIONS This invention relates to photographic processing. In one aspect this invention relates to combined bleach and fix solutions commonly known as bleach-fix solutions. in another aspect this invention relates to methods for regenerating bleach-fix solutions.

Combined bleach-fix compositions are used in processing of silver halide color photographic materials after color development to convert metallic silver to its cationic state (bleaching) and to dissolve otherwise insoluble silver salts from the photographic element (fixing). The combination of the bleaching and fixing operations into a single step simplifies processing and processing machines and decreases processing time thereby offering potential cost savings in processing and also in solution storage and handling.

in actual practice, however, the use of stable bleach-fix compositions has proven far more costly that the use of separate bleach and fixing solutions especially in large scale processing. This was due in large part to the unavailability of effective methods for regenerating bleach-fix solutions. Consequently, the use of bleach-fix compositions has been limited to special, usually high-speed processes where chemical costs are only a minor consideration and solutions can be discarded after use.

We have found a method for regenerating combined bleach-fix solutions wherein iodine is incorporated into the solution to both reoxidize spent oxidant of the bleach-fix and remove silver from the solution. The regenerated solution is effective for use as a bleach-fix in photographic processing.

Accordingly, this invention provides methods for regenerating bleach-fixes whereby costs associated with the use of bleach-fix solutions can be substantially decreased.

This invention also provides regenerated bleach-fixes and methods for using these bleach-fixes in the processing of silver halide color photographic materials.

Further, this invention provides simple methods for removing silver from used bleach-fixes containing complexed silver ions and reduced oxidant while substantially simultaneously oxidizing the reduced oxidant thereby regenerating the bleach-fix, i.e., restoring substantially all of the original bleaching and fixing capabilities of the bleach-fix.

Other advantages of the present invention will be apparent from the following disclosure.

According to one embodiment of the present invention iodine is combined with an exhausted bleach-fix solution, that is, a combined bleaching and fixing solution, which has been used to such an extent that it no longer reliably performs both its bleaching and fixing function or a combined bleaching and fixing solution which contains substantial amounts of reduced bleaching agent (oxidant) and substantial amounts of dissolved silver ions. The iodine can, for example, be added as a solid, a gas, or advantageously as a solution desirably in a water immiscible solvent. The amount of iodine used will depend to some degree of the type of bleach-fix, the extent the bleach-fix has been used, the type of photographic material processed, etc. It is desirable to use a weight of iodine somewhat in excess of the calculated weight of ionized silver present in the solution. The amount of iodine added is desirably no greater than about l.2 g. iodine per gram of silver present in the solution and advantageously no greater than about l.l8 g. iodine per gram of silver present in the solution. Lesser quantities of iodine may be desirable but usually only result in bleach-fix solutions which are not completely regenerated unless, of course, some halide has previously been generated or used in the bleach-fix itself.

The time necessary for the regeneration varies widely. When the iodine is introduced into the bleach-fix as a solid the reaction takes somewhat longer than when the iodine is added as a solution in a nonwater miscible solvent, such as benzene or chloroform. The use of water miscible solvents may be employed provided they do not deleteriously affect the basic character of the bleach-fix.

Similarly, the temperature for the regeneration step also may vary with the upper limits determined to a large degree by the stability of the bleaching and fixing agents selected.

The combined stable bleaching and fixing solution can be prepared by combining a number of silver bleaching agents, i.e., materials which oxidize silver to silver ions and silver halide fixing agents, i.e., so-called silver halide solvents.

The bleaching agents or oxidants, used in the combined bleaching and fixing solutions according to the present invention, have a reduced state sufficiently stable that degradation will not occur but which can be oxidized to the original state, that is, as it existed in a fresh bleach-fix, by reaction with molecular iodine. Examples of oxidants effective in combined bleaches and fixes are those metals which have ions of multiple oxidation states, for example, cupric ions (supplied to the solution as water soluble salts, such as cupric chloride, nitrate, sulfate, etc.); cob'altic ions (supplied to the solution as water soluble salts, such as cobaltic chloride, cobaltic ammonium nitrate, etc.); and especially ferric ions (supplied to the solution as a simple water-soluble ferric salt, e.g., ferric chloride, ferric nitrate, ferric thiocyanate, ferric oxalate, etc. or as com plex materials, such as ferricyanides, e.g., sodium ferricyanide, potassium ferricyanide, ammonium ferricyanide, etc.). Other bleaching agents include water-soluble quinones (e.g., quinone, sulfophenylquinone, chloroquinone, methoxyquinone, 2,5-dimethoxyquinone, methylquinone, etc.); complex salts of an alkali metal and a polyvalent cation with an organic acid having one of the formulas:

wherein X represents a hydrocarbon residue, oxygen, sulfur or an =NR group; R, R", R, R", and R" each represent a substitutedhydrocarbon residue and an unsubstituted hydrocarbon residue, and R represents hydrogen, an unsubstituted hydrocarbon residue and a substituted hydrocarbon residue, and wherein the polyvalent cation is selected from the class of ferric ion, cobaltic ion and cupric ions. Typical examples of the organic acids are ethylene diamine tetraacetic acid, nitrilotriacetic acid, malonic acid, ethyl malonic acid, tartaric acid, maleic acid, fumaric acid, diglycolic acid, ethyliminodipropionic acid, ethylene dithioglycolic acid, dithioglycolic acid, etc. Advantageously, the reduced oxidant contains a ferrous moiety.

The fixing agents, or silver halide solvents, utilized in the present invention include those fixing agents which do not dissolve an appreciable quantity of silver iodide usually less than a few grams per liter, ideally less than one-half gram per liter. Highly suitable fixing agents are water-soluble organic diol fixing agents containing sulfur atoms interspersed along the carbon chain (e.g., 3-thia-l-5-pentanediol, 3,6-dithia-l,8-octanediol,3 ,6,9-trithial ,l l-undecanediol,3 ,6, 9, l Ztetrathia-I l4-tetradecanediol, 9-oxa-3 ,6,9,12,l5-tretathial ,17-heptadecanediol, 3,6,9,l2,2l,30,33,36,39-nonaoxa-l5,l8,24,27- tetrathia-l,4l-hentetracontanediol, etc.). water-soluble sulfur-containing organic dibasic-acids which are especially useful, e.g., ethylene bis-thioglycolic acid, 3,6,9-trithiahendecanedioic acid, 3,6,9,lZ-tetrathiatetradecanedioic acid and their water-soluble salts (e.g., sodium salts, potassium salts, etc.), an imidazolidinthione (e.g., methyl imidazolidinthione, ethyl imidazolidinthione, etc. etc.

Addenda commonly used in bleach-fix solutions may be used in bleach-fixes which can be regenerated according to the present invention including phosphates, alkali metal bromide, ammonium bromide, amines, mercapto derivatives of 5- membered heterocyclic rings, such as mercaptotriazole, etc. The pH of the solution is usually maintained at about 7 or desirably at about 6.8, slightly on the acid side of neutral.

in one embodiment of the present invention iodine is added to a combined bleaching and fixing solution which has been utilized in processing photographic materials having colorforming couplers contained in respective layers of a multilayer photographic element. Materials of this type have been described in a number of U.S. and foreign patents, for example, in U.S. Patents 2,322,027, June 15, 1943; 2,407,210, Sept. 3, 1946; 2,474,293, June 28, 1949; 2,640,776, June 2, 1953; and 2,956,876, Oct. 18, 1960. Included are the socalled negative-positive type materials as well as reversal materials. The photographic multilayer color materials comprise elements having usually three selectively sensitive emul sion layers coated on one side of a photographic support. Sensitive layers of the elements contain color-forming couplers to form the complementary dye to which a particular layer is sensitive. in sensitive materials of this type, the uppermost layer can be blue-sensitive and normally incorporates a yellowforming coupler. The next layer generally comprises a filter layer which is yellow in color and blue absorbing and being placed under the top layer absorbs most of the blue light thus preventing unwanted blue exposure below the filter layer. The next layer is generally green-sensitive and usually incorporates a magenta-dye forming coupler. The emulsion layer adjacent to the support is then red-sensitive and according to the present invention normally contains a cyan-dye forming coupler. Sometimes multilayer photographic elements used in the present invention contain additional silver halide emulsion layers or other interlayers for specialized purposes. In photographic print materials, frequently the yellow filter layer is omitted and the arrangement of silver halide emulsion layers may be changed for the purpose of obtaining more accurate recording of the color negative.

ln the development of exposed photographic silver halide emulsion layers using the elements described above, any color-forming developer containing a primary amino group may be used. These include developers having two primary amino groups as well as those having one of the amino groups substituted or having substituents in the ring, such as the alkyl phenylene diamines. These compounds are usually used in the salt form, such as the hydrochloride or the sulfate which are more stable than the amines themselves. Suitable compounds are diethyl-p-phenylenediamine hydrochloride, monomethylp-phenylenediamine hydrochloride, dimethyl-p-phenylenediamine hydrochloride, and 2-amino-5- diethylaminotoluene hydrochloride. The p-amino phenols and their substitution products may also be used where the amino group is unsubstituted. All of these developers have an unsubstituted amino group which enables the oxidation products of the developer to couple with the color-forming compounds to form a dye image.

Generally known processing procedures can be utilized in accordance with the present invention and the regenerated bleachfix solutions of the present invention can be used interchangeably or in mixture with fresh bleach-fix.

The processing procedure usually comprises the following steps:

a. developing the film in a color developer;

b. desirably washing the developed film;

c. optionally contacting the film with an acid stop solution;

d. contacting the film with a bleach-fix solution which has been regenerated by introducing iodine into the bleachfix solution whereby reduced oxidant is reoxidized and silver iodide is precipitated and then separating the precipitate from the bleach-fix solution;

e. optionally washing the film;

f. optionally contacting the film with a stabilization solution;

and

g. drying the film.

in an especially advantageous embodiment the regenerated bleach-fixes of the present invention are utilized in processing of reversal photographic materials in which the color development is preceded by a black and white development step which, of course, involves well-known black and white developers, e.g., hydroquinone type.

The use of iodine in the indicated manner results in a method for regenerating photographic bleach-fix compositions or to restore to a used bleach-fix a substantial amount of the bleaching and fixing capabilities which it exhibited as a fresh bleach-fix, which method comprises a. combining (admixing), desirably with agitation or stirring, a bleach-fix containing: i. substantial amounts of reduced oxidant, advantageously ferrocyanide ions; and ii. substantial amounts of silver ions which in one advantageous embodiment are rendered soluble by the presence of organic diols or diacid functional groups having one or more -S-" moieties interspersed in a hydrocarbon chain separating the functional groups, highly efiicacious examples of which are 2,2- ethylenedithiadiethanol, thiadiethanol, and 2,2- ethylenedithiaacetic acid; with iodine, desirably by adding iodine as a solid or advantageously dissolved in water immiscible solvent to the bleach-fix and mixing for a sufficient period of time to allow the iodine to convert reduced oxidant to its oxidized state, e.g., ferrocyanide to ferricyanide, with the iodide formed thereby precipitating as silver iodide; and

b. separating the precipitated silver iodide from the bleachfix by centrifugation, filtration, etc.

As indicated above, substantial amounts of reduced oxidant and silver ions are provided in the normal course of processing. Silver in quantities as low as 1 gram per liter and even lower may effectively be removed in accordance with present invention and such low concentrations as well as higher concentrations are thus considered substantial amounts. The quantity of silver present in the solution to be regenerated can readily be determined with sufficient accuracy by known quantitative analytical techniques.

The following examples further illustrate our invention and/or advantages thereof:

EXAMPLE 1 The following ingredients are combined in the approximate specified amounts:

Potassium ferricyanide 65 g. Sodium ferrocyanide decahydrate 25 g. Disodium hydrogen phosphate 6 g. Sodium dehydrogen phosphate 2 g. 2,2'-ethylenedithiadiethanol 70 g.

Water to l liter to form a solution having a pH of about 6.8. To this solution is added sufficient silver nitrate (about 1.6 g.) to produce a simulated seasoned bleach-fix having a silver ion concentration of about i g. silver ion per liter of solution. To this bleachfix is added about 0.6 g. crystalline iodine.

The reaction mixture is vigorously agitated for about 2 minutes. A precipitate of silver iodide is formed which is removed by filtration. The amount of silver halide that is removed corresponds to the removal of about 0.45 g. silver. The treated solution functions surprisingly effectively as a bleach-fix for use in processing photographic materials as described hereinabove, especially with reversal color photographic materials which are processed in a conventional manner except for the use of the treated bleach-fix in lieu of a fresh bleach-fix. The ferrocyanide was stoichiometrically oxidized by the iodine to ferricyanide.

EXAMPLE 2 The procedure of example 1 is followed except that 1.18 g. iodine is added instead of 0.6 g. The quantity of silver removed as silver halide is about 0.9 g. The treated solution functions as a bleach-fix in a manner and to an extent analogous to that of example 1.

EXAMPLE 3 The procedure of example 1 is followed except that about 1.8 g. iodine is added instead of 0.6 g. The silver is removed quantitatively as silver iodide. The regenerated solution is effective in its bleaching capacity but less satisfactory in capacity as a fixing solution when compared to that of example 1.

EXAMPLE 4 EXAMPLE 5 The procedure according to example 4 is followed except that about 5.9 g. iodine is added to a liter of solution and about 4.7 g. silver is precipitated as silver iodide. The regenerated bleach-fix is as effective as that of example 1.

EXAMPLE 6 The procedure according to example 5 is followed except that 8.55 g. of iodine are added in place of 5.90 g. The results analogous to example 3 are achieved.

EXAMPLE 7 The procedure according to example 1 is followed except that 2,2'-ethylenedithiadiacetic acid is used in lieu of 2,2- ethylenedithiadiethanol. Results similar to example l are achieved.

EXAMPLE 8 The procedure according to example 1 is followed except that 200 ml. (about C.) thiadiethanol is used in lieu of 70 g. 2,2-ethylenedithiadiethanol. Results analogous to example 1 are achieved.

EXAMPLE 9 The procedure according to example 8 is followed except that 8 g. silver nitrate are used to produce a simulated seasoned bleach containing 5 g. dissolved silver per liter of solution. The addition of 5 g. iodine resulted in the precipitation of about 3.9 g. silver as silver iodide. Also, ferrocyanide is oxidized by iodine stoichiometrically to ferricyanide. The

resultant solution functions surprisingly effectively as a bleach-fix for photographic color processing.

EXAMPLE 10 A photographic bleach-fix composition containing dissolved silver and ferrocyanide and other materials in quantities generally analogous to the ingredients indicated in example 5 but silver ions resulting from the use of the solution as a bleach-fix composition is treated in accordance with the procedures outlined in example 5. Results similar to those of example 5 are achieved.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be efiected within the spirit and scope of the invention.

We claim:

l. [n a method for regenerating a photograph bleach-fix composition and using the resultant composition as a bleachfix for silver halide emulsion layers, the steps comprising:

a. combining said bleach-fix containing a substantial amount of reduced oxidant and a substantial amount of complexed silver ions, with iodine for a time sufficient to allow the iodine to oxidize the reduced oxidant and to precipitate the complexed silver ions as silver iodide, and

b. separating the silver iodide from the bleach-fix.

2. The invention according to claim I and wherein step (a) is accompanied by vigorous agitation and iodine is added to the bleach-fix as crystalline iodine.

3. The invention according to claim 1 and wherein iodine IS added to an aqueous bleach-fix in an amount up to about l.2 g. iodine per g. silver in the solution.

4. A method as in claim 1 and wherein the reduced oxidant contains a ferrous moiety.

5. A method as in claim 1 and wherein the reduced oxidant contains a ferrous moiety and the solution further contains a water soluble fixing agent containing diacid or diol functional groups separated by a carbon chain which has at least one sulfur atom interspersed in the carbon chain.

6. A method as in claim 1 and wherein iodine is added to an aqueous bleach-fix solution containing i. as a reduced oxidant, ferrocyanide ions and ii. as the complexed silver ions, silver ions rendered soluble by a compound selected from a group consisting of 2,2- ethylenedithiadiethanol, 2,2-ethylenedithiadiacetic acid, and thiadiethanol. 

2. The invention according to claim 1 and wherein step (a) is accompanied by vigorous agitation and iodine is added to the bleach-fix as crystalline iodine.
 3. The invention according to claim 1 and wherein iodine is added to an aqueous bleach-fix in an amount up to about 1.2 g. iodine per g. silver in the solution.
 4. A method as in claim 1 and wherein the reduced oxidant contains a ferrous moiety.
 5. A method as in claim 1 and wherein the reduced oxidant contains a ferrous moiety and the solution further contains a water soluble fixing agent containing diacid or diol functional groups separated by a carbon chain which has at least one sulfur atom interspersed in the carbon chain.
 6. A method as in claim 1 and wherein iodine is added to an aqueous bleach-fix solution containing i. as a reduced oxidant, ferrocyanide ions and ii. as the complexed silver ions, silver ions rendered soluble by a compound selected from a group consisting of 2,2''-ethylenedithiadiethanol, 2,2''-ethylenedithiadiacetic acid, and thiadiethanol. 